1. Field of the Invention
This invention relates to an improved structure for continuously distributing hot water evenly across the top face of a fill assembly in a crossflow water cooling tower.
2. Description of the Prior Art
Evaporative water cooling towers conventionally include a heat-exchanging fill assembly which gravitationally receives a stream of hot water to be cooled by flow of ambient derived air therethrough. Within the fill assembly, air is brought into sensible heat exchange relationship in a manner to effect the most efficient cooling of the water possible considering factors such as overall tower cost, pumping head of the water to be cooled, the water temperature range for the particular application, geographical sites of the tower. The means for inducing air flow may comprise a natural draft, hyperbolic tower structure, but, more commonly, a motor-driven fan is utilized because the hyperbolic tower requires a large amount of space as well as capital outlay. Moreover, the fan can be selectively controlled to operate only when needed to maintain the necessary air flow through the tower in relation to the air and water temperatures, whereas the natural draft tower, in contrast, must be sized for all ambient temperatures to which the tower will be subjected.
Mechanical draft cooling towers often are arranged in partitioned cells. The fill assembly of each cell is arranged in a pair of opposed, upright banks supported by tower framework, and each cell typically has a single, horizontally-disposed fan which overlies a plenum between the banks. Hot water to be cooled is delivered through piping to a distribution basin which overlies each bank of fill assembly. Subsequently, the water exits the basin in the form of a plurality of streams or sprays gravitationally delivered from metering nozzles or discharge orifices in the basic bottom and which impinge on the upper adjacent face of the fill assembly for break up into droplets or division into films for more effective heat transfer. Finally, the cooled water is gathered in a cold water collection reservoir underlying the fill assembly for ultimate return to the point of use.
It is the functional objective of the distribution basin provided in conventional towers to receive the incoming stream of hot water and direct the same toward all of the metering nozzles such that the latter are then operable to equally discharge the water evenly over the top face of the underlying fill assembly. Water flow rates within the tower can be on the order of 1,000 to 10,000 gallons a minute or more. Depending on overall tower size, the upper face of the fill assembly may be of such horizontal dimensions that some of the metering nozzles are disposed at significant distances from the inlet pipe supplying the hot water. The flow rates of this magnitude applied to an open top distribution basin of simple, U-shaped construction results in a steady-state water depth being shallower near the pipe inlet than adjacent the ends of the basin, when it is assumed that the metering nozzles are of equivalent diameter and spaced at uniform intervals. Furthermore, the kinetic energy of the water discharging from the pipe often is of such a magnitude that very turbulent hot water basin flows are experienced, possibly resulting in loss of water due to splashing. Also, turbulent flows cause unsteady water levels in the basin such that the static head applied to each nozzle is variable, rendering the nozzle discharge flow rate uneven, if not substantially unpredictable. Furthermore, high velocity flows over the nozzles can reduce nozzle flow rates and increase uneven water distribution.
In an effort to distribute the incoming hot water to all of the metering nozzles equally, prior art cooling towers have occasionally been provided with a distribution basin having an upstanding, centrally disposed partition which, in turn, has an upper weir edge. The partition has a longitudinal axis parallel to the elongated sides of the basin, and nozzles are located in the basin bottom on both sides of the partition. In operation, the incoming hot water is directed toward one side of the weir such that the chamber bounded by the partition and an adjacent basin side operates as a flume to carry water throughout the length of the latter. As the flume fills with water, the latter overflows the weir and spills into the remaining areas of the basin. As can be appreciated, water levels in this type of flume are higher than the water levels in the remainder of the basin. Consequently, the metering nozzles in the bottom of the flume are subjected to a higher static head than the remaining nozzles in the basin and, to compensate for this head difference, nozzles within the flume are typically provided with a smaller opening than the nozzles in the remaining basin area. However, such compensation requires extensive mathematical calculations for proper nozzle sizing under ideal water flow rates. Additionally, when the tower is operating under a reduced water flow such mathematical compensation is in error, often resulting in a portion of the nozzles receiving all or a significantly larger proportion of the hot water to the exclusion of a remaining portion of the metering nozzles. Obviously, such construction substantially reduces tower efficiencies.
It has also been suggested in the past to provide a distribution structure wherein a flume is positioned externally of the basin in side-by-side relationship. However, location of such a flume on the inboard side of the fill assembly adjacent the distribution basin interferes with the air pathways through the central portion of the tower. By contrast, placement of such a side-by-side flume on the outboard side of the fill assembly adjacent the basin interrupts the clean, aesthetically pleasing lines of the tower wall. In either case, this type of flume requires an additional, extensive support structure and, by necessity, thereby increases the overall size and cost of the tower correspondingly.